The CAS Registry Mumber 2900-19-8 includes 7 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 4 digits, 2,9,0 and 0 respectively; the second part has 2 digits, 1 and 9 respectively. Calculate Digit Verification of CAS Registry Number 2900-19: (6*2)+(5*9)+(4*0)+(3*0)+(2*1)+(1*9)=68 68 % 10 = 8 So 2900-19-8 is a valid CAS Registry Number.